The present disclosure relates to solid-state imaging devices and methods for fabricating the same, and more particularly to a solid-state imaging device, such as a MOS image sensor, including pixels that each include a photoelectric converter and are arranged in an array pattern, and a method for fabricating the same.
In recent years, there has been a demand for higher image quality and downsizing of solid-state imaging devices. However, the degree to which the pixel size is reduced is physically limited, and a reduction in pixel size causes a significant problem of a reduction in sensitivity.
Conventional solid-state imaging devices configured to solve such a problem have been proposed in, e.g., Japanese Patent Publication No. 2006-54252 and Japanese Patent Publication No. 2004-71817. Conventional first and second solid-state imaging devices will be described hereinafter with reference to FIGS. 15 and 16.
As illustrated in FIG. 15, the conventional first solid-state imaging device includes a photoelectric converter 102 formed on an SOI (silicon on insulator) substrate 100. Specifically, the SOI substrate 100 includes a plurality of silicon layers 101a and 101b, and a buried insulating film 103 formed between the silicon layers 101a and 101b. The silicon layer 101b on the buried insulating film 103 includes the photoelectric converter 102. The buried insulating film 103 is configured to reflect long wavelength light, and improving the absorption efficiency of long wavelength light in the photoelectric converter 102 enhances the sensitivity. Since the structure of the conventional first solid-state imaging device enhances the sensitivity, the shallow photoelectric converter 102 can be formed, thereby reducing optical crosstalk between adjacent pixels.
As illustrated in FIG. 16, similarly to the conventional first solid-state imaging device, the conventional second solid-state imaging device includes a reflector structure 202 under a semiconductor layer 200 including a photoelectric converter 201. Specifically, the reflector structure 202 is, not a single insulating film, but a layered structure of a silicon dioxide (SiO2) film and a silicon nitride (SiN) film, and enhances the sensitivity of the photoelectric converter 201 to long wavelength light. Although not shown, a convex lens and a concave lens are formed on the photoelectric converter 201 to allow light to enter the photoelectric converter 201 in a direction perpendicular to the surface of the semiconductor layer 200, thereby reducing optical crosstalk.